Lectins bind to carbohydrate moieties, e.g. acetylglucosamine, that are ubiquitous in the mammalian extracellular matrix. This suggests the possibility that lectins may be used to coat the matrix and limit further binding of collagen, elastin, and other connective tissue components to carbohydrate groups. The aggregation of large amounts of matrix constituents, as occurs in fibrosis, may therefore be subject to limitation by the introduction of lectins.
This hypothesis was tested in our laboratory. Elastic fiber matrix prepared from cultured rat lung mesothelial cells (1,2) was first treated with tomato lectin (lycopersicon esculentum), then covered with hyaluronan (HA), which normally protects the matrix from degradation by elastases. It was found that lectin treatment abolished the protective effect of HA and facilitated breakdown of the elastic fiber matrix by elastase.
Since the binding of HA to the elastic fibers is analogous to fibrosis in that it involves deposition of new matrix material (HA) over existing matrix, the addition of lectin may provide a means of counteracting this process and preventing the formation of scar tissue.
This potential anti-fibrotic activity may not be specific to tomato lectin, but instead be related to a general characteristic of lectins, i.e. binding to carbohydrate moieties. Consequently, lectins, as a class of agents, may prevent the deposition of newly synthesized matrix components, and therefore be useful in treating diseases such as pulmonary fibrosis and cirrhosis of the liver.